Studies are being made of the development of the eye lens in the chicken and the normal mouse embryo and in mouse strains with genetic mutations leading to lens abnormalities (aphakia; Cataract-Fraser; lens rupture; eye-less). Emphasis is given to morphogenetic and biochemical changes taking place in the earliest phase of lens formation ("lens induction"), and in particular to cellular proliferation and specific protein synthesis. Histological, autoradiographic and immunofluorescent techniques are used, as well as chromatography and electrophoresis. It is hoped that the studies will lead to better understanding of the genetic regulation of lens differentiation and of the causes of hereditary eye defects.